Silicone oil, on account of its safety, has long been used as a base oil in various compositions in many fields, including cosmetics.
In particular, low viscosity silicone oil of not more than 100 mm2/s is attracting attention with a view to extensive use in cosmetic skin care and make-up on account of its outstanding extensibility, fresh feeling and safety.
However, if a pasty composition without fluidity is prepared using low viscosity silicone oil as a base oil, the addition amount of thickener must be increased, so it is difficult to obtain a smooth, uniform composition, and as the low viscosity silicone oil easily separated and was released from the composition so obtained, its stability was low. In order to solve this problem, the use of organic materials as thickeners for low viscosity silicone oil has been proposed, examples being dextrin fatty acid esters (Tokkai Sho 62-121764, 62-143971, 62-143970, 63-159489) sucrose fatty acid esters (Tokkai Sho 63-235366), trimethylsilyl polyvinyl alcohol and trimethylsilyl polysaccharides (Tokkai Sho 62-240335), fatty acid ester group-containing cellulose ether (Tokkai Sho 63-260955), and organically-modified clay minerals (Tokkai Sho 62-45656, 62-54759, 63-72779).
However, when these organic or inorganic materials are used as thickeners, there is a problem that the inherent fresh feeling and high extensibility of the low viscosity silicone oil, decline.
A method of obtaining a uniform pasty composition was therefore proposed using a specific organopolysiloxane polymer as a thickener, and treating it with a low viscosity silicone oil under a shear force (Tokkai Hei 02-43263).
In the field of cosmetics, not only oil but water is often blended as a required component of the composition. In such a case, although a surfactant is used according to conventional methods, it is difficult to distribute the silicone oil and water uniformly and stably, and although the silicone thickener disclosed in Tokkai Hei 02-43263 has excellent thickening qualities with regard to silicone oil, it has the disadvantage that when water is blended, it does not disperse uniformly. In addition, some surfactants irritate the skin, which is undesirable.
In order to solve this problem, Tokkai Hei 04-272932 and 05-140320 propose introducing a polyoxyalkylene group into the molecule of the silicone thickener. Although the composition disclosed therein has excellent emulsifying characteristics, it has the disadvantage that if the composition is stored over a long period of time, the pH falls, and the emulsion emits an unpleasant odor.
A polyether-modified organopolysiloxane can be purified by treating it with an acidic solution (Tokko Hei 07-91389) or by treating unsaturated groups by hydrogenation (Tokkai Hei 07-330907). If these purification methods are applied to this crosslinking type polymer, when treating with corrosive aqueous acids such as hydrochloric acid solution, if the apparatus used does not have a glass lining, the apparatus may be corroded. Moreover, even if the odor can be reduced, the fall in pH cannot be suppressed.
If hydrogenation treatment is performed, heavy metal catalysts such as palladium and nickel are required, but as these catalysts cannot be removed by filtration, heavy metal catalysts may remain in the composition and are therefore unsuitable for use in cosmetics.
As a result of intensive studies to resolve the above disadvantage, the Inventor found that in a composition comprising a crosslinking type organopolysiloxane polymer wherein the crosslinks are formed by hydrophilic organic groups (polyoxyalkylene chains) and a liquid oil, a composition with good storage stability and which did not emit an unpleasant odor could be obtained by adding an acidic substance to this polymer, performing heat treatment, neutralizing with a basic substance and removing volatile components, and thereby arrived at the present invention.
It is therefore an object of this invention to provide a paste-like composition comprising a crosslinking type organopolysiloxane polymer and an oil which has an emulsifying function, which has excellent storage stability and does not emit an unpleasant odor, to provide a method of manufacturing same, and to provide a cosmetic material containing this composition.